Cooler for a suspension damper

ABSTRACT

A method and apparatus are disclosed for cooling damping fluid in a vehicle suspension damper unit. A damping unit includes a piston mounted in a fluid cylinder. A bypass fluid circuit having an integrated cooling assembly disposed therein is fluidly coupled to the fluid cylinder at axial locations that, at least at one point in the piston stroke, are located on opposite sides of the piston. The cooling assembly may include a cylinder having cooling fins thermally coupled to an exterior surface of the cylinder and made of a thermally conductive material. The bypass channel may include a check valve that permits fluid flow in only one direction through the bypass channel. The check valve may be remotely operated, either manually or automatically by an electronic controller. A vehicle suspension system may implement one or more damper units throughout the vehicle, controlled separately or collectively, automatically or manually.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 61/449,045 (Atty. Dkt. No. FOXF/0054USL), filed Mar. 3, 2011,which is herein incorporated by reference in its entirety. Embodimentsof this application may be used with embodiments of U.S. ProvisionalPatent Application Ser. No. 61/296,826 (Atty. Dkt. No. FOXF/0043USL),filed Jan. 20, 2010, U.S. patent application Ser. No. 12/684,072 (Atty.Dkt. No, FOXF/0032US), filed Jan. 7, 2010, and U.S. patent applicationSer. No. 13/010,697 (Atty. Dkt. No. FOXF/0043USP1), filed Jan. 20, 2011,each of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to vehicle suspensions and, morespecifically, to a cooler assembly for a suspension damper.

2. Description of the Related Art

Vehicle suspension systems typically include a spring component orcomponents and a damping component or components. Typically, mechanicalsprings, like helical springs, are used with some type of viscousfluid-based damping mechanism, the spring and damper being mountedfunctionally in parallel. In some instances, features of the damper orspring are user-adjustable, such as by adjusting the air pressure in agas spring. A damper may be constructed by placing a vented dampingpiston in a fluid-filled cylinder. As the damping piston is pushed intothe cylinder, fluid is compressed and passes slowly through the vents inthe piston, which are often covered by shim stacks to provide fordifferent operational characteristics in compression or extension.

One disadvantage with conventional damping components is that thermalvariations in operating conditions can cause the damping characteristicsof the damping components to change. The environment that the dampingcomponents are operated in can vary widely, from arctic conditions onsnowmobiles to desert conditions on off-road vehicles. Even within agiven environment, the temperature fluctuation can change wildly duringdifferent parts of the day. Furthermore, as the damping components aresubject to repetitive cycles, such as when a truck is being driven overrough terrain in the desert, the oil contained within the dampingcylinder may heat up due to work performed on the oil by the dampingpiston. As the oil heats up, the viscosity of the oil will decrease,thereby allowing oil to flow more easily through the vented dampingpiston. Similarly, heat from nearby engine components may alsocontribute to the temperature of the oil. At high temperatures, such asgreater than 400° F., the heat can lead to a degradation of rubbersealing elements within the damping components that could causepermanent damage to the vehicle suspension as oil is no longer sealedwithin the damping components.

As the foregoing illustrates, what is needed in the art are improvedtechniques for controlling operating temperatures of a suspensiondamper.

SUMMARY OF THE INVENTION

One embodiment of the present disclosure sets forth a vehicle suspensiondamper that includes a cylinder containing a piston assembly comprisinga piston and piston rod, a working fluid within the cylinder, apassageway through the piston allowing and limiting a flow rate of theworking fluid through the piston in at least one direction, and a bypasschannel comprising a fluid pathway between a first side of the pistonand a second side of the piston. The bypass channel includes a coolingchamber disposed within the fluid pathway.

Yet another embodiment of the present disclosure sets forth a vehiclesuspension system that includes one or more of the vehicle suspensiondampers, set forth above.

One advantage of some disclosed embodiments is that the viscous fluid inthe suspension damper is continuously circulating through the coolingchamber during the stroking of the piston, thereby transferring excessheat to the air surrounding the cooling chamber. This continuous cyclehelps to keep the fluid temperature at levels that will not harm thedamping components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side elevation view of a suspension damping unit,according to one example embodiment;

FIG. 2 is a sectional side elevation view of a suspension damping unitthat implements an integrated reserve fluid reservoir, according toanother example embodiment;

FIG. 3 is a sectional side elevation view of a suspension damping unit,according to yet another example embodiment;

FIGS. 4, 5, and 6 are enlarged views showing a remotely operable needlevalve in various positions, according to some example embodiments;

FIG. 7 is a schematic diagram illustrating a sample circuit used toprovide remote control of a bypass valve using a vehicle's powersteering fluid, according to one example embodiment; and

FIG. 8 illustrates a system for controlling the bypass channels based onfour variables: rod speed, rod position, vehicle speed, and fluidtemperature, according to one example embodiment.

DETAILED DESCRIPTION

Integrated damper/spring vehicle shock absorbers often include a damperbody surrounded by or used in conjunction with a mechanical spring orconstructed in conjunction with an air spring or both. The damper oftenconsists of a piston and shaft telescopically mounted in a fluid filledcylinder. The damping or working fluid may be, for example, hydraulicoil. A mechanical spring may be a helically wound spring that surroundsor is mounted in parallel with the damper body. As used herein, theterms “down” “up” “downward” upward” “lower” “upper” and otherdirectional references are relative and are used for reference only.

FIG. 1 is a sectional side elevation view of a suspension damping unit100, according to one example embodiment. The damper includes a cylinder102 with a rod 107 and a piston 105. In one embodiment, the dampingfluid meters, from one side to the other side of piston 105, by passingthrough flow paths 110, 112 formed in the piston 105. In the embodimentshown, shims 115, 116 are used to partially obstruct the flow paths 110,112 in each direction. By selecting shims 115, 116 having certaindesired stiffness characteristics, the damping effects can be increasedor decreased and damping rates can be different between the compressionand rebound strokes of the piston 105. For example, shims 115 areconfigured to meter rebound flow from the rebound portion 103 of thecylinder 102 to the compression portion 104 of the cylinder 102. Shims116, on the other hand, are configured to meter compression flow fromthe compression portion 104 of the cylinder 102 to the rebound portion103 of the cylinder 102. In one embodiment, shims 116 are not includedon the rebound portion side, rather the compression flow path 110 isabsent, leaving the piston essentially “locked out” in the compressionstroke without some means of flow bypass (e.g., damping fluid mustbypass the piston 105 rather than traverse ports in the piston 105).Note that piston apertures (not shown) may be included in planes otherthan those shown (e.g. other than apertures used by paths 110 and 112)and further that such apertures may, or may not, be subject to the shims115, 116 as shown (because for example, the shims 115, 116 may beclover-shaped or have some other non-circular shape).

The upper portion of the rod 107 (opposite the piston 105) may besupplied with an eyelet 109 to be mounted to one part of the vehicle,while the lower part of the damping unit 100 is shown with an eyelet 108that may be attached to another portion of the vehicle, such as theframe, that moves independently of the first part. A spring member (notshown) is often mounted to act between the same portions of the vehicleas the damper. As the rod 107 and piston 105 move into cylinder 102(during compression), the damping fluid slows the movement of the twoportions of the vehicle relative to each other due to the incompressiblefluid moving through the shimmed path 110 (past shims 116) provided inthe piston 105 and/or through a bypass path 156 via the metered bypassassembly 150, as will be described herein. As the rod 107 and piston 105move out of the cylinder 102 (during extension or “rebound”), fluidmeters through shimmed path 112, and/or a fluid bypass, and the flowrate and corresponding rebound rate is controlled by corresponding shims115 or other flow restriction mechanisms.

In one embodiment as shown in FIG. 1, a bypass assembly 150 is designedto permit damping fluid to travel from a first side of the piston to theother side without traversing shimmed flow path 110 that may otherwisebe traversed in a compression stroke of the damper. The bypass assembly150 includes a tubular body 155 that is fluidly coupled with the dampercylinder 102 through bypass entry aperture 160 and bypass exit aperture165. The flow of fluid through the bypass assembly 150 is shown bybypass path 156. A needle-type throttle and check valve 180 (hereinafter“check valve 180” or “throttle/check valve 180”, used interchangeablyherein), allowing flow in one direction and checking flow in theopposite direction, is located proximate to bypass exit aperture 165.The check valve 180 sets flow resistance through the bypass assembly 150during the compression stroke and restricts fluid from entering thebypass assembly 150 during the rebound stroke of the damper piston 105.In one embodiment, the check valve 180 is spring loaded and biasedclosed. The initial compression force of the biasing spring 182 isadjusted via adjuster 183 thereby allowing a user to preset the needlevalve opening pressure and hence the compression damping fluid flow ratethrough the bypass assembly 150. The biasing force of the needle valvespring 182 is overcome by fluid pressure in the tubular body 155 causingthe throttle/check valve 180 to open against the spring during acompression stroke.

The bypass entry aperture 160 is located towards a lower end of thedamper cylinder 102 (i.e., the end of the damper cylinder 102 proximatethe piston 105 towards the end of the compression stroke). In oneembodiment, as selected by design, the bypass assembly 150 will notoperate after the piston 105 passes the bypass entry aperture 160 nearthe end of a compression stroke or located elsewhere in the stroke asdesired. This “piston position sensitive” feature ensures increaseddamping will be in effect near the end of the compression stoke to helpprevent the piston from approaching a “bottomed out” position (e.g.impact) in the cylinder 102. In some instances, multiple bypasses areused with a single damper and the entry pathways for each may bestaggered axially along the length of the damper cylinder 102 in orderto provide an ever-increasing amount of damping (and less fluid flowthrough the bypass assembly 150) as the piston 105 moves through itscompression stroke and towards the top of the damping cylinder 102.Certain bypass damper features are described and shown in U.S. Pat. Nos.6,296,092 and 6,415,895, each of which is incorporated herein, in itsentirety, by reference.

In one embodiment, the bypass assembly 150 includes a fluid (e.g.hydraulic or pneumatic) fitting disposed at an end of the check valve180, described below in conjunction with FIGS. 4-6. The fluid fitting isintended to carry a control signal in the form of fluid pressure to thevalve 180 in order to adjust the needle valve opening pressure of thecheck valve 180. Thus, the throttle/check valve 180 may be adjusted byremote control from a simple operator-actuated switch located in thepassenger compartment of the vehicle. As such, an operator may remotelycontrol the throttle opening and hence bypass pressure, therebycontrolling the stiffness of the damper. In one embodiment, fluidpressure for controlling the check valve 180 is provided by thevehicle's own source of pressurized hydraulic fluid created by, forexample, the vehicle power steering system. In another embodiment,pneumatic pressure is used to control the check valve 180 where thepneumatic pressure is generated by an on-board compressor andaccumulator system and conducted to the check valve 180 via a fluidconduit. In yet another embodiment, a linear electric motor (e.g.solenoid), or other suitable electric actuator, is used, in lieu offluid pressure, to manipulate and adjust the check valve 180 preload. Insuch electrical embodiments, the solenoid is wired (e.g. via electricalconduit) into the vehicle electrical system and switched, for example,in the operator cockpit to adjust the check valve 180.

As also shown in FIG. 1, damping unit 100 also includes a second bypasspath 256 operable in a rebound stroke of the piston 105. It isnoteworthy that the second bypass could operate in the compressionstroke, the rebound stroke, or both the compression and rebound strokes,depending on the configuration of the check valve 180 or omissionthereof. In one embodiment, the second bypass path 256 comprises acooling assembly 200 that comprises a cylinder body 202, a lower seal212 and an upper seal 214 connected by a connecting rod 206. The lowerseal 212 may be threaded onto the connecting rod 206 and slid into thelower end of the cylinder body 202. The upper seal 214 may then bethreaded onto the upper end of the connecting rod 206 to form a fluidreservoir 208 inside the cylinder body 202. The lower seal 212 includesa fluid inlet port 215 and a fluid outlet port 216 allowing dampingfluid to pass from the rebound portion 103 of the cylinder 102, throughthe cylinder body 202 of the cooling assembly 200, and back to thecompression portion 104 of the cylinder 102. The lower seal 212 andupper seal 214 may form a fluid-tight seal against the inner surface ofthe cylinder body 202 using one or more sealing elements such as arubber o-ring. A plurality of radial cooling fins 204 may be formed onthe outer surface of the cylinder body 202, which increases the externalsurface area of the cylinder body 202, thereby increasing the heattransfer effectiveness of the cooling assembly 200. In one embodiment,the cooling fins 204 may be made from a material having good thermalconductivity such as, for example, aluminum or copper, or alloysthereof. In another embodiment, the cylinder body 202 is made from amaterial having good impact resistance, strength, and fatigue life suchas aluminum or aluminum alloys. The cylinder 202 and cooling fins 204may be constructed from a single piece of material or may be an assemblyof multiple parts constructed from separate pieces and/or types ofmaterials having the same or suitable desired properties such as thermalconductivity, strength, and toughness.

The fluid inlet port 215 is fluidly coupled with the rebound portion 103of the cylinder 102 through a cooling entry aperture 260 in cylinder102. The fluid outlet port 216 is fluidly coupled with the compressionportion 104 of the cylinder 102 through a cooling exit aperture 265 incylinder 102. The cooling entry aperture 260 and the cooling exitaperture 265 may be positioned axially near the top and bottom ofcylinder 102, respectively. In one embodiment, the cooling assembly 200may be connected to the cylinder 102 via flexible hydraulic hoses 221,222 and hydraulic fittings. In another embodiment, the cooling assembly200 may be connected to the cylinder 102 via hydraulic tubes made ofrigid material such as stainless steel or aluminum. Although shownproximate to damping unit 100, in some embodiments, cooling assembly 200may be located remotely from the damping unit 100, such as near a fan byan air intake for a vehicle.

A needle-type throttle and check valve 280 (hereinafter “check valve280” or “throttle/check valve 280”, used interchangeably herein),allowing metered flow in one direction and checking flow in the oppositedirection, is located proximate to cooling exit aperture 265. In oneembodiment, the check valve 280 is similar to check valve 180 in thebypass assembly 150 and sets flow resistance through the coolingassembly 200 during the rebound stroke and restricts fluid from enteringthe cooling assembly 200 during the compression stroke of the piston105. In one embodiment, the check valve 280 is spring loaded and biasedclosed. The initial compression force of the biasing spring 282 isadjusted via valve adjuster 283 thereby allowing a user to preset theneedle valve opening pressure and hence the rebound damping fluid flowrate through the cooling assembly 200. The biasing force of the needlevalve spring 282 is overcome by fluid pressure in the hydraulic hose 222causing the check valve 280 to open during a rebound stroke.

In one embodiment, the cooling assembly 200 includes a fluid (e.g.hydraulic or pneumatic) fitting disposed at an end of the check valve280, as shown in FIGS. 4-6. The fluid fitting is intended to carry acontrol signal in the form of fluid pressure to the valve adjuster 283in order to adjust the needle valve opening pressure of the check valve280. The check valve 280 may be adjusted by remote control from a simpleoperator-actuated switch located in the passenger compartment of thevehicle. Alternatively, the check valve 280 may be controlledautomatically by an electronic control module or a thermostat configuredto monitor the temperature of the damping fluid and decrease the needlevalve opening pressure via valve adjuster 283 when the temperature isabove a threshold temperature to increase fluid flow through the coolingassembly 200 or increase the needle valve opening pressure via valveadjuster 283 when the temperature is below a threshold temperature todecrease fluid flow through the cooling assembly 200. Operation of thecheck valve 280 may be generally as described in relation to check valve180.

In one embodiment, the fluid outlet port 216 is fluidly coupled to thefluid reservoir 208 formed in the cylinder body 202 by a tube 220 thatforces fluid that flows through the fluid outlet port 216 to be drawnfrom the far end of the cylinder body 202, opposite the end of thecylinder body 202 that includes both the fluid inlet port 215 and thefluid outlet port 216. By forcing fluid to be drawn from a point at thefar end of the cylinder body 202, hot fluid that enters the cylinderbody 202 at the fluid inlet port 215 will transfer heat to the cylinderbody 202 that is dissipated via convection over the cooling fins 204.Thus, fluid drawn down through the tube 220 is cooler than fluid thatenters the cylinder body 202 at the fluid inlet port 215. The tube 220may be insulated to prevent hot fluid entering the cylinder body 202 atthe fluid inlet port 215 from transferring heat to the fluid leaving thecylinder body 202 through the fluid outlet port 216. In anotherembodiment, the tube 220 may be coupled to the fluid inlet port 215 suchthat fluid entering the cylinder body 202 must first flow through thetube 220 to the far end of the cylinder body 202. In this embodiment,there is no tube connected to the fluid outlet port 216 such that coolerfluid at the bottom of the cylinder body 202 exits through the fluidoutlet port 216.

In operation, damping unit 100 may be compressed, where piston 105 isforced towards the lower end of the cylinder body 102. The fluidpressure in the compression portion 104 of the cylinder body 102increases as piston 105 moves into the cylinder body 102. Consequently,fluid is forced through the flow path 110 and past shims 116 into therebound portion 103 of the cylinder body 102. If the fluid pressure inthe compression portion 104 of the cylinder body 102 is larger than theneedle valve opening pressure of check valve 180, then fluid may alsoflow into the rebound portion 103 of the cylinder body 102 via thebypass assembly 150. It will be noted that, in one embodiment, checkvalve 280 prevents fluid from flowing from the compression portion 104of the cylinder body 102 through the cooling exit aperture 265 and intothe cooling assembly 200. Once damping unit 100 has reached the end ofthe compression stroke, the piston 105 reverses direction and begins therebound stroke as the damping unit 100 returns to an uncompressed state.

During the rebound stroke, the fluid pressure in the rebound portion 103of the cylinder body 102 increases as piston 105 moves up through thecylinder body 102. Fluid is forced through flow path 112 and shims 115into the compression portion 104 of the cylinder body 102. If the fluidpressure in the rebound portion 103 of the cylinder body 102 is largerthan the needle valve opening pressure of check valve 280, then fluidmay also flow from the rebound portion 103 of the cylinder body 102 intothe cooling assembly 200 via hydraulic hose 221 and into the compressionportion 104 of the cylinder body 102 via the hydraulic hose 222. As thefluid passes through cylinder body 202 of the cooling assembly 200, heatfrom the fluid is transferred to the air surrounding the coolingassembly 200.

It will be appreciated that the effectiveness of the cooling assembly200 is dependent on the external surface area of the cylinder 202.Therefore, in order to increase the effectiveness of the coolingassembly 200, the length of the cylinder 202 may be adjusted to matchthe heat transfer specification for a given application. For example, ashort cylinder body 202 may be effective in temperate climates whereas along cylinder body 202 may be effective in a desert environment. In someembodiments, the cooling assembly 200 may be configured to work duringthe compression stroke of piston 105 rather than the rebound stroke byswitching the locations of the cooling inlet port 260 and the coolingoutlet port 265.

In one embodiment, the damper unit 100 includes only one bypass circuitcomprising a cooler assembly 200 as described herein, where the bypasscircuit includes no check valve, and where the piston 105 further omitsfluid paths 110, 112 therein such that all damping fluid is forced toflow through the cooler assembly 200 during both the compression strokeand the rebound stroke. In some embodiments, one or both of check valves180 and 280 may not be included. In such embodiments, the size of entryapertures 160, 260 and exit apertures 165, 265 may be designed torestrict the amount of fluid flow through the bypass assembly 150 or thecooling assembly 200. In other embodiments, one or both of check valves180 and 280 may be replaced with a non-adjustable check valve thatallows fluid flow in only one direction via a fixed cracking pressure(Le the minimum upstream pressure differential at which the valve willoperate).

FIG. 2 is a sectional side elevation view of a suspension damping unit100 that implements an integrated reserve fluid reservoir 300, accordingto another example embodiment. The reserve fluid reservoir 300 storesdamping fluid in a reservoir portion 128 of a reservoir cylinder 125that is in fluid communication with the compression portion 104 of thecylinder 102. The reservoir 300 receives and supplies reserve dampingfluid as rod 107 moves in and out of the cylinder 102, accounting forthe small change in volume of the damping fluid caused by the intrusionof the rod 107 into the rebound portion 103 of the cylinder 102. Thereservoir 300 includes a floating piston 130 moveably mounted within thecylinder 125, with a volume of gas 55 on a backside (“blind end”) of thefloating piston 130, the gas being compressible as the reservoir portion128 of the cylinder 125 fills with fluid due to movement of the rod 107.Certain features of reservoir type dampers are shown and described inU.S. Pat. No. 7,374,028, which is incorporated herein, in its entirety,by reference. The reservoir portion 128 of the reservoir cylinder 125 isfluidly coupled to the compression portion 104 of the cylinder 102 via atube 50 connected to a fluid port near the lower end of cylinder 102.For added cooling, an exterior surface of the reservoir 300 may includecooling fins as described herein generally in relation to the coolingbypass circuit.

FIG. 3 is a sectional side elevation view of a suspension damping unit400, according to yet another example embodiment. As shown in FIG. 3,damping unit 400 is a position-sensitive shock absorber including acylinder 404 having an interior 406, first and second ends 408, 410 anddefining an axis 412. A floating piston 414 divides interior 406 into adamping fluid chamber 416 and a gas chamber 418. Gas chamber 418 can bepressurized through a pressurization port 420. Gas chamber 418 andfloating piston 414 accommodate the volume of oil or other damping fluidwithin chamber 416 displaced by the movement of shaft 419 into thedamping fluid chamber 416. A vented piston 422 is movably mounted withinthe cylinder 404 for moving between the first and second ends 408, 410of the cylinder 404. A number of axially separated bypass openings 424,426, 428, 430, 432 are formed through the cylinder 404. A bypasscylinder 436 surrounds cylinder 404 and defines a cylindrical bypasschannel 438. Bypass openings 424, 426 and 432 are always open andfluidly couple the damping fluid chamber 416 and the bypass channel 438to permit some damping fluid to bypass the vented damping piston 422when the piston is positioned between these bypass openings thusreducing the damping during this portion of the stroke. In oneembodiment, bypass openings 428, 430 are covered by expandable bands440, 442 positioned within annular grooves formed in the outer surfaceof cylinder 404. Bands 440, 442 act as check valve elements that permitfluid flow from the damping fluid chamber 416 to the annular bypasschannel 438 but restrict, and typically prevent, fluid flow in theopposite direction. Thus, the shock absorber will exhibit differentdamping characteristics along the same segment of the stroke dependingupon whether the stroke is the compression stroke or the rebound stroke.

In one embodiment, cooling fins 450 are formed on an outer surface ofthe bypass cylinder 436. The cooling fins 450 may be made from amaterial exhibiting good thermal conductivity such as copper oraluminum, as well as alloys thereof. Damping fluid passing through thebypass channel 438 is cooled as heat from the damping fluid istransferred to air flowing over the cooling fins 450 of the bypasscylinder 436. The cooler damping fluid is then circulated back into thedamping fluid chamber 416 through bypass openings 424, 426, and 432.

FIGS. 4, 5, and 6 are enlarged views showing a remotely operable needlevalve 500 in various positions, according to some example embodiments.In some embodiments, valve 500 may be used in place of check valve 180or check valve 280 to provide a remote-operation capability to thebypass channels of damping unit 100. In FIG. 4, the valve 500 is in adamping-open position (fluid path shown by arrow 501) permitting thebypass channel to operate and let fluid flow through the bypass channel.The valve 500 includes a valve body 504 housing a movable piston 505which is sealed within the body. Three fluid communication points areprovided in the body including an inlet 502 and outlet 503 for fluidpassing through the valve 500 as well as an inlet 525 for control fluidas will be described herein. Extending from a first end of the piston505 is a shaft 510 having a cone-shaped member 512 (other shapes such asspherical or flat, with corresponding seats, will also work suitablywell) disposed on an end thereof. The cone-shaped member 512 istelescopically mounted relative to, and movable on, the shaft 510 and isbiased in an extended position (FIG. 5) due to a spring 515 coaxiallymounted on the shaft 510 between the member 512 and the piston 505. Dueto the spring biasing, the cone-shaped member 512 normally seats itselfagainst a seat 517 formed in an interior of the body 504. In the dampingopen position shown however, fluid flow through the bypass has providedadequate force on the member 512 to urge it backwards, at leastpartially loading the spring 515 and creating fluid path 501 from thebypass channel into the damper cylinder as shown in FIG. 1. Thecharacteristics of the spring 515 are typically chosen to permit thevalve 500 (e.g. member 512) to open at a predetermined bypass pressure,with a predetermined amount of control pressure applied to inlet 525.For a given spring 515, higher control pressure at inlet 525 will resultin higher bypass pressure required to open the valve 500 which decreasesfluid flow through the bypass channel. In one embodiment, the valve 500is open in both directions when the valve piston 505 is “topped out”against valve body 504. In another embodiment however, when the valvepiston 505 is abutted or “topped out” against valve body 504 the spring515 and relative dimensions of the valve 500 still allow for the conemember to engage the valve seat thereby closing the valve. In suchembodiment backflow through the bypass channel is always substantiallyclosed and cracking pressure from fluid flow through the bypass channelis determined by the pre-compression in the spring 515. In such anembodiment, additional fluid pressure may be added to the inlet throughport 525 to increase the cracking pressure of valve 500 and therebydecrease fluid flow through the bypass channel over that value providedwhen the spring 515 is “topped out.” It is generally noteworthy thatsome or all of the bypass channels (or channel) on a given suspensionunit may be configured to allow or restrict both compression damping andrebound damping bypass.

FIG. 5 shows the valve 500 in a closed position (which it assumes duringa rebound stroke of the damper). As shown in FIG. 5, the cone shapedmember 512 is seated against seat 517 due to the force of the spring 515and absent an opposite force from fluid entering the valve along thebypass channel. As member 512 telescopes out, a gap 520 is formedbetween the end of the shaft 510 and an interior of member 512. A vent521 is provided to relieve any pressure formed in the gap. With thefluid path 501 closed, fluid communication is substantially shut offfrom the bypass channel into the valve body and a “dead-end” path isshown by arrow 519 which prevents fluid from flowing into the bypasschannel.

Inlet 525 is formed in the valve body 504 for operation of the valve. Inone embodiment inlet 525 may be pressurized to shift the valve 500 to athird or “locked-out” position. In FIG. 6, the valve 500 is shown in thelocked-out position, thereby preventing fluid flow through the bypasschannel in either direction, regardless of whether the damping unit 100is in a compression stroke or a rebound stroke. In the embodiment shown,the control inlet 525 provides a fluid path 530 to a piston surface 527formed on an end of the piston 505, opposite the cone-shaped member 512.Specifically, activating pressure is introduced via inlet 525 to movethe piston 505 and with it, member 512 toward seat 517. Sufficientactivating pressure fully compresses the spring 515 (substantial stackout) and/or closes the gap 520 thereby closing the cone 512 against theseat 517, sealing the bypass channel to both compression flow in onedirection and rebound flow in the other direction. In the embodimentshown, the valve 500 can be shifted to the third, locked-out positionfrom either the first, open position or the second, closed position.Note that, when in the “locked out” position, the valve 500 as shownwill open to fluid flow through the bypass channel when the fluid flowpressure acting over the surface area of the seated valve cone 512exceeds the inlet 525 pressure acting over the surface area of thepiston 505. Such inlet 525 pressure may be selected to correspond to adesired overpressure relief value or “blow off” value, thereby allowingfluid to flow through the bypass channel under “extreme” conditions evenwhen the bypass is “locked out”.

The valve 500 is intended to be shifted to the locked-out position withcontrol fluid acting upon piston 505. In one embodiment, the activatingpressure via inlet 525 is adjusted so that the valve 500 is closed tofluid flowing through the bypass channel in one direction (e.g.,opposite bypass paths 156, 256) but with the spring 515 not fullycompressed or stacked out. In such a position, a high enough fluid force(e.g. fluid pressure in the bypass channel) will still open the valve500 and allow fluid to pass through the valve 500. In one arrangement,the activating pressure, controlled remotely, may be adjusted betweenlevels where the lock-out is not energized and levels where the lock-outis fully energized. The activating pressure may also be adjusted atintermediate levels to create more or less fluid flow through the bypasschannel. The activating pressure may be created by hydraulic orpneumatic input or any other suitable pressure source.

In one example, the valve 500 is moved to a locked-out position and thebypass feature (i.e., compression bypass or cooling bypass) of thedamping unit 100 is disabled by remote control from a simpleoperator-actuated switch located in the passenger compartment of thevehicle. In one embodiment, fluid pressure for controlling (e.g.locking-out) the valve 500 is provided by the vehicle's on-board sourceof pressurized hydraulic fluid created by, for example, the vehiclepower steering system. In another embodiment, pneumatic pressure is usedto control (e.g. close) the valve 500 where the pneumatic pressure isgenerated by an on-board compressor and accumulator system and conductedto the valve 500 via a fluid conduit. In yet another embodiment, alinear electric motor (e.g. solenoid), or other suitable electricactuator, is used, in lieu of the aforementioned inlet 525 pressure, tomove the “piston” axially within valve body. A shaft of the electricactuator (not shown) may be fixed to the piston such that axial movementof the shaft causes axial movement of the piston which in turn causesmovement of the cone 512 (and compression of the spring as appropriate).In such embodiments, the electric actuator is configured to “push” thepiston towards a closed position and to “pull” the piston away from theclosed position depending on the direction of the current switchedthrough the actuator.

FIG. 7 is a schematic diagram illustrating a sample circuit 600 used toprovide remote control of a bypass valve 500 using a vehicle's powersteering fluid (although any suitable fluid pressure source may besubstituted for reservoir 610 as could an electrical current source inthe case of an electrically actuated valve), according to one exampleembodiment. As illustrated in FIG. 7, a fluid pathway 605 having acontrol-operated valve 602 therein runs from a fluid (or current)reservoir 610 that is kept pressurized by, in one embodiment, a powersteering pump (not shown) to a check valve 500 that is operable, forexample, by a user selectable dash board control 615. The valve 502permits fluid to travel to the inlet 525 of the check valve 500, therebyallowing a user or electronic controller to adjust the needle valveopening pressure of the valve 500. In one embodiment, the control 615 isa three position switch that allows a user to remotely set the needlevalve opening pressure of the valve 500 by increasing or decreasing thepressure of fluid in pathway 605. In another embodiment, the control 615is a rheostat that allows a user to set the pressure of fluid in pathway605 via a linearly actuated pressure regulator 602 based on the positionof the rheostat. While FIG. 7 is simplified and involves control of asingle valve 500, it will be understood that the valve 502 could beplumbed to simultaneously provide a signal to two or more check valves500 operable with two or more vehicle damping units and/or with a singledamping unit having multiple valves 500. Additional switches couldpermit individual operation of separate damper check valves 500, whetheron separate dampers or on the same damper, depending upon an operator'sneeds. While the example of FIG. 7 uses fluid power for operating thevalve 500, a variety of means are available for remotely controlling avalve. For instance, a source of electrical power from a 12 volt batterycould be used to operate a solenoid member. The signal can be either viaa physical conductor or an RF signal (or other wireless such asBluetooth, WiFi, ANT) from a transmitter operated by the controller 615to a receiver operable on the valve 500.

While the examples illustrated relate to manual operation of the valve500, other embodiments contemplate automated operation of valve(s) 500based upon specific parameters. The remotely operated bypass assembly150 and cooling assembly 200 check valves can be used in a variety ofways with many different driving and road variables. In one example, thebypass assembly 150 is controlled based upon vehicle speed inconjunction with the angular location of the vehicle's steering wheel.In this manner, by sensing the steering wheel turn severity (angle ofrotation), additional damping can be applied to one damper or one set ofdampers on one side of the vehicle (suitable for example to mitigatecornering roll) in the event of a sharp turn at a relatively high speed.In another example, a transducer, such as an accelerometer measuresother aspects of the vehicle's suspension system, like axle force and/ormoments applied to various parts of the vehicle, like steering tie rods,and directs change to the bypass valve 180 positioning in responsethereto. In another example, the bypass valve 180 can be controlled atleast in part by a pressure transducer measuring pressure in a vehicletire and adding damping characteristics to some or all of the wheels inthe event of, for example, an increased or decreased pressure reading.In one embodiment, the damper bypass assembly 150 or bypass channels(including, as desired, the cooling assembly 200 type bypass describedherein) are controlled in response to braking pressure (as measured forexample by a brake pedal sensor or brake fluid pressure sensor oraccelerometer). In still another example, a parameter might include agyroscopic mechanism that monitors vehicle trajectory and identifies a“spin-out” or other loss of control condition and adds/reduces dampingto some or all of the vehicle's dampers in the event of a loss ofcontrol to help the operator of the vehicle to regain control. In stillyet another example, the fluid flow rate through the cooling assembly200 can be controlled, at least in part, based on the temperature of thedamping fluid.

FIG. 8 illustrates, for example, a system including four variables: rodspeed, rod position, vehicle speed, and fluid temperature, according toone example embodiment. Any or all of the variables shown may beconsidered by processor 702 in controlling the valve 500. Any othersuitable vehicle operation variable may be used in addition to or inlieu of the variables 705, 710, 715, and 720 such as for example pistonrod compression strain, eyelet strain, vehicle mounted accelerometerdata or any other suitable vehicle or component performance data. In oneembodiment, a suitable proximity sensor or linear coil transducer orother electro-magnetic transducer is incorporated in the dampingcylinder 102 to provide a sensor to monitor the position and/or speed ofthe piston 105 (and suitable magnetic tag) with respect to the cylinder102. In one embodiment, the magnetic transducer includes a waveguide anda magnet, such as a doughnut (toroidal) magnet that is joined to thecylinder and oriented such that the magnetic field generated by themagnet passes through the piston rod and the waveguide. Electric pulsesare applied to the waveguide from a pulse generator that provides astream of electric pulses, each of which is also provided to a signalprocessing circuit for timing purposes. When the electric pulse isapplied to the waveguide a magnetic field is formed surrounding thewaveguide. Interaction of this field with the magnetic field from themagnet causes a torsional strain wave pulse to be launched in thewaveguide in both directions away from the magnet. A coil assembly andsensing tape is joined to the waveguide. The strain wave causes adynamic effect in the permeability of the sensing tape which is biasedwith a permanent magnetic field by the magnet. The dynamic effect in themagnetic field of the coil assembly due to the strain wave pulse,results in an output signal from the coil assembly that is provided tothe signal processing circuit along signal lines. By comparing the timeof application of a particular electric pulse and a time of return of asonic torsional strain wave pulse back along the waveguide, the signalprocessing circuit can calculate a distance of the magnet from the coilassembly or the relative velocity between the waveguide and the magnet.The signal processing circuit provides an output signal, either digitalor analog, proportional to the calculated distance and/or velocity. Sucha transducer-operated arrangement for measuring rod speed and velocityis described in U.S. Pat. No. 5,952,823, which is incorporated byreference herein in its entirety.

While a transducer assembly located at the damper measures rod speed andlocation, a separate wheel speed transducer for sensing the rotationalspeed of a wheel about an axle includes housing fixed to the axle andcontaining therein, for example, two permanent magnets. In oneembodiment the magnets are arranged such that an elongated pole piececommonly abuts first surfaces of each of the magnets, such surfacesbeing of like polarity. Two inductive coils having flux conductive coresaxially passing therethrough abut each of the magnets on second surfacesthereof, the second surfaces of the magnets again being of like polaritywith respect to each other and of opposite polarity with respect to thefirst surfaces. Wheel speed transducers are described in U.S. Pat. No.3,986,118, which is incorporated by reference herein in its entirety.

In one embodiment, as illustrated in FIG. 8, a logic unit 702 withuser-definable settings receives inputs from the rod speed 710 andlocation 705 transducers as well as the wheel speed transducer 715. Thelogic unit is user-programmable and depending on the needs of theoperator, the unit records the variables and then if certain criteriaare met, the logic circuit sends its own signal to the bypass assembly150 to either close or open (or optionally throttle) the check valve180. Thereafter, the condition of the bypass valve 180 is relayed backto the logic unit 702. In another embodiment, the logic unit 702 withuser-definable settings receives inputs from the temperature sensor 720,and adjusts the control signal to the cooling assembly 200 to eitherclose or open (or optionally throttle) the check valve 280. Thereafter,the condition of the check valve 280 is relayed back to the logic unit702.

It will be appreciated that the logic shown in FIG. 8 assumes a singledamper but the logic circuit is usable with any number of dampers orgroups of dampers. For instance, the dampers on one side of the vehiclecan be acted upon while the vehicles other dampers remain unaffected.

The foregoing embodiments, while shown in configurations oftencorresponding to off-road truck shock absorbers, are equally applicableto bicycle or motorcycle shocks or front forks or other vehicle shockabsorbers. While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments may be implemented withoutdeparting from the scope of the disclosure, the scope thereof beingdetermined by the claims that follow.

1. A vehicle suspension damper comprising: a cylinder containing apiston assembly comprising a piston and piston rod; a working fluidwithin the cylinder; and a bypass circuit connecting a first side of thepiston and a second side of the piston, wherein the bypass circuitincludes a cooling chamber.